Fire-resistant coating composition



Patented Apr. 13, 1948 2,439,895 I FIRE-RESISTANT COATING COMPOIITION Martin Leatherman, Hyattsville, Md.

No Drawing. Application June 30, 1945, Serial No. 802,647

3 Claims. (01. 260-303) (Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) This application is a continuation-in-part of my co-pending application Serial Number 447,871, filed June 20, 1942, which issued as U. S. Patent No. 2, 407,668 on September 17, 1946.

This application is made under the act of March 3, 1883, as amended by the act of April 30, 1928, and the invention herein described and claimed, if patented, may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment to me of any royalty thereon.

This invention relates to fire retarding or fire resistant coatings for fibrous materials in filamentary or foraminous, reticulated form, whether I woven, felted or in layers and is applicable to cotton, rayon, wool, silk and the like.

My invention is adaptable to make various types of finished articles. It can be used to produce a water repellant but porous finish or it can be used to produce a rubber-like coating which is impermeable to air. If the fabric to be coated is immersed in my composition and then squeezed lightly, a thin fabric such as 80 square print cloth shows numerous tiny pinholes which permit free passage of air, but which offer considerable resistance to the passage of water. If the dipped fabric is immediately brushed on one side with my composition, an elastic flexible rubberlike and impermeable finish results which adheres tightly to the dipped and squeezed fabric. The unbrushed side retains its soft fabric-like appearance and feel. If, however, the dipped and lightly squeezed fabric is again dipped and excess composition scraped off without squeezing, an adherent rubber-like finish is imparted to both faces of the fabric.

The flexibility, elasticity and generally rubberlike appearance of my composition is imparted by the presence of suitable amounts of acrylate or methacrylate ester polymers. These polymers have little or no flame resistance but contribute the desirable physical properties. Another resinous constituent of my composition is either polyvinyl chlo'ride or a co-polymer of vinyl acetate and vinyl chloride. The addition of even a, few parts of acrylate or methacrylate ester polymer to the polyvinyl chloride or co-polymer of vinyl acetate and vinyl chloride imparts much improved elasticity and toughness to my coating composition.

A third constituent of my composition is zinc carbonate. It is the interaction of the vinyl polymer with the zinc carbonate which imparts fire resistance to the fibrous materials when coated with my composition. When the coated material is subjected to ignition temperatures, the vinyl polymer decomposes with evolution of hydrochloric acid which, in addition to possessing excellent flame preventing properties, reactswith the zinc carbonate to liberate carbon dioxide and catalytically active zinc oxide. The zinc oxide acts as a dehydration catalyst in the case of cellulosic materials to split the carbohydrate into water and carbon, thus assisting in preventing flaming.

A fourth constituent of my composition may be some form of opaque pigment which while not required as a fiameprooflng ingredient, may be desirable to screen out light which in some cases acts detrlmentally on the vinyl polymer constituent. A fifth constituent is a suitable plasticizer or softener. a, preferred form of which is tricresyl phosphate although certain chlorinated diphenyls, dibutyl phthalate, triphenyl phosphate or any other compatible plasticizer or mixture of plasticizers may also be used.

In practicing my invention a preferred method is to dissolve the resinous constituents together with the plasti'clzer in compatible solvents and suspend the zinc carbonate and pigments in the solution by any suitable dispersion method. The efifect obtained is in large measure determined by the proportion of solvent or diluent present.

The following example of a composition embodying my invention is given by way of illustration but not of limitation.

Example 15 lbs. of vinyl acetate-vinyl chloride copolymer, 5 lbs. of n-butyl methacrylate, 10 lbs. tricresyl phosphate, 7 lbs. triphenyl phosphate, 5.8 lbs. of zinc carbonate, 4.2 lbs. of inert pigment, 27 lbs. of acetone, 27 lbs. of the solvent known by the trade name of Solvesso No. 2, 8.7 lbs. of mineral spirits and /2 lb. of pentachlorphenol.

As additional ingredients I also employ such fungicides as pentachlorphenol, copper naphthenate, cadmium naphthenate, zinc naphthenate, zinc pentachlorphenate, halogenated phenyl phenates and the like in amounts approximating 1% of the weight of the fibrous material.

In the above formula I may substitute the methyl, ethyl or propyl polymerized ester of acrylic acid or methacrylic acid for n-butyl methacrylate and likewise I may use a polyvinylchloride resin instead of the co-polymer or vinyl acetate and vinyl chloride. Depending upon the degree of flame resistance desired, I may vary the relative proportions of the resinous components with respect to each other. The less methacrylate or acrylate resin present with respect to vinyl chloride resin the greater the degree of flame resistance. However, if the relative amount of the former is dropped too low, adhesion, flexibility and elasticity are lessened undesirably in view ofthe presence of the suspended solids. On the other hand, if too much of the acrylate or methacrylate resin is substituted for the vinyl resin fire resistance is reduced. In general it would not be desirable to use more methacrylate or acrylate resin than vinyl resin in the composition. a

The coating characteristics are largely determined by the viscosity of the coating composition. If the viscosity is reduced by addition of solvent, an impregnated type of finish is obtained upon evaporation of solvent, that is, the fibrous material absorbs the composition and the pores remain open. With increased viscosity, penetrative qualities of the composition are decreased and a continuous film or coating of a rubber-like nature covers the whole surface of the fabric. In this form the coating is impervious to air. An advantage of this continuous fllm lies in the fact that, because of the thermoplasticity of my composition, the coated fabric can be lapped and caused to form a strong bond by the application of heat.

It is understood that the example above cited can be varied with respect to the proportions of all constituents. As stated before, I may vary the relative proportions of vinyl chloride polymer and methacrylate or acrylate polymer. I may vary the proportion of zinc carbonate to vinyl polymer. A preferred range is from 1 part Zinc carbonate to 1 parts'of vinyl polymer to 1 part zinc carbonate to 3 parts of vinyl polymer. The absolute amount of inert pigment used will vary with the severity of weather exposure and with the type of pigment used. The proportion of p1asticizer will vary with the degree of flexibility desired and with the type of plasticizer used. Finally the solvent employed can be any individual solvent or blend of solvents which is compatible with the synthetic resin mixture in my composition. Among the solvents which can be employed at least in part are acetone, ethanol, butanol, iso- 4 butanol. diacetone alcohol, xylol, toluol, naphtha or Stoddard solvent.

It is also understood that the fire resistant qualities of my coating composition do not reside in the acrylate or methacrylate polymers. 11 desired, for certain purposes, these may be omitted completely, in which case, provided the plasticizer is also omitted, a composition is obtained which may be used to provide a fireproof, non-flexible coating for cotton yarn and fabrics.

Applicant is informed that Solvesso No. 2 is a blend of aromatic solvents, of which the major constituent is toluol, having'a specific gravity of 0.858 and a boiling point range from 265 F. to 375 F.

I claim:

1. A composition for rendering fabric rotand fire-resistant, comprising the following materials in substantially the proportions stated: 15 lbs. vinyl acetate vinyl chloride copolymer, 5 lbs. nbutyl methacrylate polymer, 10 lbs. tricresyl phosphate, 5.8 lbs. zinc carbonate, 27 lbs. acetone, 27 lbs. of a solvent consisting mainly of aromatic compounds having a specific gravity of about 0.858 and a boiling range from 265' F. to 375 F., 8.7 lbs. mineral spirits, 4.2 lbs. inert pigment, and lb. pentachlorphenol.

2. A composition for rendering fabric rotand fire-resistant, comprising the following materials in substantially the proportions stated: 15 lbs. vinyl acetate vinyl chloride copolymer, 5 lbs. nbutyi methacrylate polymer, 10 lbs. tricresyl phosphate, 5.8 lbs. zinc carbonate, 27 lbs. acetone, 27 lbs. of a solvent consisting of aromatic compounds having a specific gravity of about 0.858 and a boiling range from 265 F. to 375 F., and 8.7 lbs. mineral spirits.

3. A composition for rendering fabric rotand fire-resistant, comprising the following materials in substantially the proportions stated: 15 lbs. vinyl acetate vinyl chloride copolymer, 5 lbs. nbutyl methacrylate polymer, 10 lbs. tricresyl phosphate, 5.8 lbs. zinc carbonate, 27 lbs. acetone, 27

' mineral spirits.

MARTIN LEATHERMAN. 

